Magnesium reacts faster with more concentrated hydrochloric acid than with more dilute hydrochloric acid.
Which statement explains why?
The acid particles have more energy, so each collision is harder.
The activation energy is lower in the more concentrated acid.
The acid particles move faster, so they collide with more force.
There are more acid particles in the same volume, so collisions are more frequent.
122 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.